For loading two-factor authentication secrets. Or anything else you can think of that has too much information to convey with a short link. If you are directing people to a web site using QR codes then you're doing it wrong. Well, wrong now that everyone has realized just how limited QR codes are.
I do for any printed media. It makes it easier for people to look up the corresponding electronic version of a document. QR code has its uses, but tends fail when misused. QR code is best when interacting with it is strictly optional.